Fuse holder assembly

ABSTRACT

A fuse holder assembly which is particularly adapted to be utilized in conjunction with the protection system for the primary side of an oil-filled transformer assembly, wherein the fuse holder is mounted on a plate, the plate being supported on the face of the transformer casing. The fuse holder extends from the plate through an aperture in the transformer housing to support the fusing elements below the level of the cooling liquid within the transformer housing. The fusing elements are a current limiting fuse and a weaklink fuse which are mechanically supported by the fuseholder and which can both be withdrawn from the transformer casing with the fuseholder, to permit inspection and replacement.

United States Patent [191 Russell et al.

[ Oct. 28, 1975 1 FUSE HOLDER ASSEMBLY [75] Inventors: William H.Russell, Forest Park,

Ga.; Peter Mayer, Versailles, Ky.

[52] US. Cl. 317/15; 317/14 H; 337/202;

' 337/257 [51] Int. Cl. H0211 7/04 [58] Field of Search 317/15, 14 R, 14C, 14 H, 317/40 A; 337/144, 145, 162, 186, 193, 202, 207, 208, 229, 231,412, 414

3,701,926 10/1972 Risk 317/15 3,721,942 3/1973 Conway 339/75 R 3,798,5833/1974 Charbonneau et al. 337/202 Primary Examiner-J. D. MillerAssistant ExaminerPatrick R. Salce Attorney, Agent, or Firm-Everett R.Casey [5 7] ABSTRACT A fuse holder assembly which is particularlyadapted to be utilized in conjunction with the protection system for theprimary side of an oil-filled transformer assembly, wherein the fuseholder is mounted on a plate, the plate being supported on the face ofthe transformer casing. The fuse holder extends from the plate throughan aperture in the transformer housing to support the fusing elementsbelow the level of the cooling liquid within the transformer housing.The fusing elements are a current limiting fuse and a weaklink fusewhich are mechanically supported by the fuseholder and which can both bewithdrawn from the transformer casing with the fuseholder, to permitinspection and replacement.

7 Claims, 4 Drawing Figures U.S. Patent Oct 28, 1 9 75 Sheet 1 of23,916,259

-U.S. Patent Oct. 28, 1975 Sheet 2 of2 FUSE HOLDER ASSEMBLY CROSSREFERENCE This invention is related to those of US. Pat. No. 3,699,490granted Oct. 17, 1972, and of US. Pat. No. 3,701,926 granted Oct. 31,1972, and is further related to those in the United States patentapplication of Ar- BRIEF SUMMARY OF THE INVENTION This invention relatesto an improved mechanism for electrically fusing liquid cooledelectrical induction equipment such as power and distributiontransfomers. The invention is of particular usefulness in protectingpole type, pad mounted and underground oil-filled dis tributiontransformers. For protection under a broad range of fault conditions,the combination of an oil immersible current limiting fuse and on oilirnmersible weaklink fuse, of commercially available types, is supportedinternally of the transformer housing and immersed in liquid coolantwithin that housing, and in the preferred use, the fuses are seriallyconnected with the primary windings of the transformer. Since theweaklink fuse responds to oil temperature, it reacts to secondary loadsand faults, and as a result the oilirnmersed combination can providesecondary fault control, high-energy internal fault control, highcurrent internal fault control, overload control, tank temperaturecontrol, and oil temperature control.

The fuse combination is mounted on a fuse holder member which controlsits immersed position relative to the other components of thetransformer. The fuse holder and fuse combination can be withdrawnthrough a normally covered access opening in the transformer housing forfield inspection and replacement of one or both of the fuses.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of atransformer assembly illustrating the use of the fuse holder assemblyembodying the principles of the present invention;

FIG. 2 is an elevational view of the fuse holder assembly used in thetransformer of FIG. 1;

FIG. 3' is a sectional view taken substantially along the line 3-3 ofFIG. 2; with the view being tilted on the sheet; and

FIG. 4 is an end view taken in the direction of the labeled arrow inFIG. 2.

DESCRIPTION The transformer of FIG. 1 includes a housing including acasing closed by a cover 12 bolted or otherwise secured thereon. Thetransformer, which is conventional, includes internal componentsincluding primary and secondary windings (not shown) immersed in asuitable dielectric coolant such as oil 14. The casing 10 is assumed tobe approximately square in cross section, having a front wall or plate16 and side walls 18. A fuse holder assembly 20 is majorly immersed inthe coolant 14 and projects into a throat assembly 22 formed on theexterior of the wall 16 of the casing 10. Throat assembly 22 comprises aweldment welded or otherwise secured to the front plate 16 to form aliquid-tight throat or cavity surrounding an opening 24 (FIG. 2) in thewall 16. Throat assembly 22 is itself open on its outer face, as at 26,with that opening being selectively closable by a gasketed cover plate28 which may be secured to the throat assembly 22 by means such as astud and nut assembly 30. If the dielectric liquid level is above thatof the bottom portion of the opening 24, it should be lower than theopening 26.

A fuse holder tube or support and guide member 32 is disposed within thecasing 10 and projects through opening 24 to a position proximateopening 26. Tube 32 which is of insulative material such as glass fiberreinforced epoxy. It can be formed of other insulative materials and maybe molded, extruded or otherwise formed. In the illustrated arrangement,tube 32 is generally square in cross section, tubular, and open at bothends. In one face, tube 32 is provided with an elongated slotted opening34 extending from its outermost end to a point 33 essentially midway ofits length for a purpose to be noted.

Tube 32 is rigidly supported with respect to the transformer casing. Inthe illustrated embodiment of the invention, this is accomplished byproviding both forward and aft supports. The forward support includes ascrew 36 (FIG. 3) threaded through the wall of tube 32 into a supportlug 38 which is welded or otherwise secured to the front plate 16, tothe throat assembly 22, or to both. The aft support comprises a supportbracket 40, which may be of glass fiber reinforced epoxy or otherwise,and which is bolted or otherwise secured both to the side wall 18 and tothe fuse holder tube 32. Tube 32 constitutes a support and guide memberto support the withdrawable elements essentially over the entirety oftheir path of withdrawal and insertion movements as well as in theirfully inserted positions.

A fuse holder or fuse attachment device is removably disposed within thetube 32. Fuse holder 42, which may be molded or otherwise formed ofplastic or other dielectric material, includes a neck portion 44 the endof which threadedly accepts a pull-out eye 46. At its lower (rightward)end, neck 44 terminates in a flanged shoulder portion 48. The bodyportion 50 of the fuse holder extends rightwardly from the shoulder 48and is hollow from the shoulder 48 rearwardly, to accept a currentlimiting fuse 52. At its innermost or forward end, the cavity 51 withinbody 50 is provided with integral position defining stops 54 (FIG. 3)for locating the end of fuse 52 at its point of maximum insertion.

A metallic end bracket 56, of folded T-shape, has a cross-arm portionwhich is secured to the fuse holder 42 such as by screws 58 (FIG. 2)which threadedly engage body portion 50. The apertures in end bracket56, which are engaged by screws 58 are preferably elongated to permitadjustment during assembly.

End bracket 56 is further provided with a depending leg portion to whicha nut 60 (FIG. 3) is welded or otherwise secured. Nut 60 threadedlyaccepts the threaded stud 62 which is formed on commercially availableforms of current limiting fuses 52. When a fuse 52 is replaced, the newfuse is simply inserted into the cavity within body 50 of the fuseholder 42 (from the right) until stud 62 engages nut 60, and is thenrotated, by hand, to thread stud 62 into nut 60, the right-hand end ofthe current limiting fuse 52 projecting from the fuse holder 42 tofacilitate that assembly.

The lower or right-hand end of the current limiting fuse 52 is providedwith the customary terminal stud 64 upon which is threaded a metallicmale contact 66. Contact 66 engages a tulip contact finger assembly 68,the projecting fingers of which are-compelled into a good electricalengagement with contact 66 by means of a garter-spring 70.

Spring assembly 68 is secured to an end bracket 72 by means of a machinescrew 74 which also serves as the line side connector. End bracket 72(FIGS. 2 and 3) is provided with projecting side arms 76 which embraceand areriveted or otherwise secured to the tube disengaged from thecontact assembly 68, and the entire assembly translated out of thehousing. It will be observed that the slot 34 in the tube 32 permits theweaklink fuse 80, with its brackets 82 and 84 and with its male contactelement 92, to be freely moved out of the tube and through the openings24 and 26 (FIG. 2).

32. It will be observed that the end bracket 72 does not fully close thelower .end of tube 32 or impede the effective flow of coolant thereinto.

A leaf spring assembly, comprising a plurality of leaf springs 78, issecured to the lower end of tube 32 in a position to engage and guidethe lower or leading end of the current limiting fuse 52.

A weaklink fuse 80 is provided with integral angled support brackets 82and 84. Support bracket 82 is screwed or otherwise detachably connectedto end bracket 56 and that end of weaklink fuse 80 is electricallyconnected to bracket 56, and hence to stud 62, and hence. to one end ofthe current limiting fuse 52.

weaklink fuse support bracket 84 (FIG. 2) is screwed or otherwisedetachably connected to a plate 86 which is in turn screwed or otherwiseattached to the body portion 50 of the fuse holder 42. Plate 86 isprovided with an upstanding leg 88 (FIG. 3) to constitute a contact. Leg88 is apertured to accept a screw 90 threadedly engaging a male contactmember 92. Male contact member 92 engages a tulip spring contactassembly 94 similar to that previously described, and that contactassembly is in turn fastened to a support bracket 96 by means of a screwand nut assembly 98 which also serves as the load side connection.Bracket 96 is riveted or otherwise secured to the fuse holder tube 32.

As a result of the noted connections, power connected to the line sideconnection 74 by means of a suitable conductor is conducted throughcurrent limiting fuse 52, stud 62, bracket 56, weaklink fuse 80, bracket84, bracket88, male contact 92, contact assembly 94, load sideconnecting stud 98 and, through a suitable conductor, to the primarywinding of the transformer.

Current limiting fuse 52 and weaklink fuse 80 may be of any suitable,appropriately rated, commercially available types such as thosemanufactured by Kearney-National, Inc. In general, current limitingfuses tended-duration low-current fault conditions, to the possiblepoint of blowing up. The weaklink fuses, on the other hand, are lesssatisfactory on high fault currents, perform well under low-currentfault conditions. Accordingly, a coordinated series combination of thetwo can provide highly improved full-range fault protection. In thepresent utilization, the weaklink fuse senses, ormay sense, oiltemperature.

To inspect or replace either of the fuses, the cover plate 28 is removedby unscrewing nuts 30. The pullout eye may then be engaged with ahotstick (shotgun stick or hookstick) and a force exerted to translatethe fuse assembly outwardly along its longitudinal axis. The malecontact 92 will thereupon be disengaged from the contact assembly 94 andthe male contact 66 will be The current limiting fuse may be replaced,if necessary, in the manner above noted, with the addition oftransferring'the male contact 66 to the replacement fuse. The weaklinkfuse may be replaced, if necessary, by unscrewing its brackets 82 and 84and replacing it with a replacement fuse.

Tile fuse assembly including the fuse holder 42 with the fuses in place,is then reinserted through the opening 26 into the fuse holder tube 32and shoved downwardly into the illustrated seated position, theengagement between the portion 50 of the fuse holder (FIG. 4) and theinner wall of the tube 32 insuring proper orientation of the parts. Inview of the magnitude of the currents which are carried, forcibleengagement should be made between the male contacts 92 and 66 and theirrespective contact assemblies 94 and 68. However, if the requisiteseating is not achieved during such reinsertion, provision is made, inthe preferred arrangement, for insuring an adequate degree of seating.This is accomplished by establishing the dimensions such that upon thereplacement of cover plate 28, and the tightening of nuts 30, theengagement between that cover plate and an improperly extending pull outeye 46 will exert a force on the assembly to drive the male contacts 92and 96 into proper electrical engagement with their respective contactassemblies.

What is claimed is:

1. In a transformer assembly having a housing having a line terminal, awinding assembly supported in the housing and having a primary windingterminal, and a cooling liquid within the housing for cooling thewinding, the combination of means defining-a separate fuse assemblyaccepting opening in said housing above the level of the cooling liquidspaced from "the line terminal, means removably attachable to saidhousing for closing said opening, a fuse holder member, first securingmeans on said fuse holder for detachably securing thereon a currentlimiting fuse, second i securing means for removably supporting aseparate weaklink fuse on the combination of said fuse holder. memberand the current limiting fuse, said first and second. securing meanspermitting separate replacement of the current limiting fuse and of theweaklink. fuse, support and guide means rigidly supported in saidhousing in a fixed position and adjacent said opening, said fuse holdermember and said support and guide means supporting the current limitingand the weaklink fuses below the level of and immersed in the coolingliquid, means for detachably electrically interconnecting the currentlimiting and the weaklink fuses, means for permitting the withdrawal ofsaid fuse holder member including the current limiting and weaklinkfuses from the housing through the opening therein, and means includingsaid support and guide means for guiding said fuse holder memberincluding the separate current limiting and weaklink fuses during thewithdrawal, reinsertion and use thereof, saidrneans for permitting thewithdrawal of said fuse holder member comprising an eye on said fuseholder engageable by a hotstick only after said means for closing saidopening has been removed.

means for automatically effecting detachment when said fuse holdermember is withdrawn from said support .and guide means.

3. The combination of claim 2 further including means for insuringre-engagement of said quick detachable connector means upon thereplacing of said fuse holder member in said support and guide means.

4. The combination of claim 3 in which said means for insuringre-engagement includes said eye and said means for closing said opening.

5. In a transformer assembly having a housing having a line terminal, awinding assembly supported in the housing and having a primary windingterminal, and a cooling liquid within the housing for cooling thewinding, the combination of means defining a separate fuse assemblyaccepting opening in said housing above the level of the cooling liquidspaced from the line terminal, means removably attachable to saidhousing for closing said opening, a fuse holder member, first securingmeans on said fuse holder for detachably securing thereon a currectlimiting fuse, second securing means for removably supporting a separateweaklink fuse on the combination of said fuse holder member and thecurrent limiting fuse, said first and second securing means permittingseparate replacement of the current limiting fuse and of the weaklinkfuse, support and guide means rigidly supported in said housing in afixed position, said fuse holder member and said support and guide meanssupporting the current limiting and the weaklink fuses below the levelof and immersed in the cooling liquid, means for detachably electricallyinterconnecting the current limiting and the weaklink fuses, means forpermitting the withdrawal of said fuse holder member including theseparate current limiting and weaklink fuses from the housing throughthe opening therein, and means including said support and guidemeans-for guiding said fuse holder member including the current limitingand weaklink fuses during the withdrawal, reinsertion and use thereof,said support and guide means comprising a rigid tubular insulativemember supported by the housing, and said fuse holder being insertablein said tubular member.

6. The combination of claim 5 in which said fuse holder has a tubularportion for sheathing a portion of the current limiting fuse and contactmeans within said tubular portion for removably securing one of thefuses within said tubular portion.

7. In a transformer assembly having a housing having a line terminal, awinding assembly supported in the housing and having a primary windingterminal, and a cooling liquid within the housing for cooling thewinding, the combination of means defining a separate fuse assemblyaccepting opening in said housing above the level of the cooling liquidspaced from the line terminal, means removably attachable to saidhousing for closing said opening, a current limiting fuse, a fuse holdermember, first securing means on said fuse holder for detachably securingthereon said current limiting fuse, a weaklink fuse, second securingmeans for removably supporting said separate weaklink fuse on thecombination of said fuse holder member and said current limiting fuse,said first and second securing means permitting separate replacement ofsaid current limiting fuse and of said weaklink fuse, support and guidemeans rigidly supported in said housing in a fixed position, said fuseholder member and said support and guide means supporting said currentlimiting and said weaklink fuses below the level of and immersed in thecooling liquid, means for detachably electrically interconnecting saidcurrent limiting and said weaklink fuses, means for permitting thewithdrawal of said fuse holder member including said separate currentlimiting and weaklink fuses from the housing through the openingtherein, and means including said support and guide means for guidingsaid fuse holder member including said current limiting and weaklinkfuses during the withdrawal, reinsertion and use thereof, said supportand guide means comprising a rigid tubular insulative member supportedby the housing, and said fuse holder being insertable in said tubularmember.

1. In a transformer assembly having a housing having a line terminal, awinding assembly supported in the housing and having a primary windingterminal, and a cooling liquid within the housing for cooling thewinding, the combination of means defining a separate fuse assemblyaccepting opening in said housing above the level of the cooling liquidspaced from the line terminal, means removably attachable to saidhousing for closing said opening, a fuse holder member, first securingmeans on said fuse holder for detachably securing thereon a currentlimiting fuse, second securing means for removably supporting a separateweaklink fuse on the combination of said fuse holder member and thecurrent limiting fuse, said first and second securing means permittingseparate replacement of the current limiting fuse and of the weaklinkfuse, support and guide means rigidly supported in said housing in afixed position and adjacent said opening, said fuse holder member andsaid support and guide means supporting the current limiting and theweaklink fuses below the level of and immersed in the cooling liquid,means for detachably electrically interconnecting the current limitingand the weaklink fuses, means for permitting the withdrawal of said fuseholder member including the current limiting and weaklink fuses from thehousing through the opening therein, and means including said supportand guide means for guiding said fuse holder member including theseparate current limiting and weaklink fuses during the withdrawal,reinsertion and use thereof, said means for permitting the withdrawal ofsaid fuse holder member comprising an eye on said fuse holder engageableby a hotstick only after said means for closing said opening has beenremoved.
 2. The combination of claim 1 further including connector meansfor connecting the current limiting fuse to one of the transformerterminals, and connector means for connecting the weaklink fuse to theother one of the transformer terminals, and in which both of saidconnector means are quick detachable connector means for automaticallyeffecting detachment when said fuse holder member is withdrawn from saidsupport and guide means.
 3. The combination of claim 2 further includingmeans for insuring re-engagement of said quick detachable connectormeans upon the replacing of said fuse holder member in said support andguide means.
 4. The combination of claim 3 in which said means forinsuring re-engagement includes said eye and said means for closing saidopening.
 5. In a transformer assembly having a housing having a lineterMinal, a winding assembly supported in the housing and having aprimary winding terminal, and a cooling liquid within the housing forcooling the winding, the combination of means defining a separate fuseassembly accepting opening in said housing above the level of thecooling liquid spaced from the line terminal, means removably attachableto said housing for closing said opening, a fuse holder member, firstsecuring means on said fuse holder for detachably securing thereon acurrect limiting fuse, second securing means for removably supporting aseparate weaklink fuse on the combination of said fuse holder member andthe current limiting fuse, said first and second securing meanspermitting separate replacement of the current limiting fuse and of theweaklink fuse, support and guide means rigidly supported in said housingin a fixed position, said fuse holder member and said support and guidemeans supporting the current limiting and the weaklink fuses below thelevel of and immersed in the cooling liquid, means for detachablyelectrically interconnecting the current limiting and the weaklinkfuses, means for permitting the withdrawal of said fuse holder memberincluding the separate current limiting and weaklink fuses from thehousing through the opening therein, and means including said supportand guide means for guiding said fuse holder member including thecurrent limiting and weaklink fuses during the withdrawal, reinsertionand use thereof, said support and guide means comprising a rigid tubularinsulative member supported by the housing, and said fuse holder beinginsertable in said tubular member.
 6. The combination of claim 5 inwhich said fuse holder has a tubular portion for sheathing a portion ofthe current limiting fuse and contact means within said tubular portionfor removably securing one of the fuses within said tubular portion. 7.In a transformer assembly having a housing having a line terminal, awinding assembly supported in the housing and having a primary windingterminal, and a cooling liquid within the housing for cooling thewinding, the combination of means defining a separate fuse assemblyaccepting opening in said housing above the level of the cooling liquidspaced from the line terminal, means removably attachable to saidhousing for closing said opening, a current limiting fuse, a fuse holdermember, first securing means on said fuse holder for detachably securingthereon said current limiting fuse, a weaklink fuse, second securingmeans for removably supporting said separate weaklink fuse on thecombination of said fuse holder member and said current limiting fuse,said first and second securing means permitting separate replacement ofsaid current limiting fuse and of said weaklink fuse, support and guidemeans rigidly supported in said housing in a fixed position, said fuseholder member and said support and guide means supporting said currentlimiting and said weaklink fuses below the level of and immersed in thecooling liquid, means for detachably electrically interconnecting saidcurrent limiting and said weaklink fuses, means for permitting thewithdrawal of said fuse holder member including said separate currentlimiting and weaklink fuses from the housing through the openingtherein, and means including said support and guide means for guidingsaid fuse holder member including said current limiting and weaklinkfuses during the withdrawal, reinsertion and use thereof, said supportand guide means comprising a rigid tubular insulative member supportedby the housing, and said fuse holder being insertable in said tubularmember.